Blue Bell plant's positive listeria tests date back to March 2013

The Food and Drug Administration released inspection reports showing Blue Bell had evidence of listeria bacteria in its Oklahoma plant as far back as March 2013.

The Food and Drug Administration released the results of its investigation into the ice cream company's plants in Alabama, Oklahoma and Texas.

The Oklahoma plant had the most issues, according to the FDA. It said there were 16 different positive tests for listeria from March 2013 through Jan. 2015, according to the report.

The FDA said the company continued to make and sell ice cream despite the positive tests.

Three people have died from listeria-tainted Blue Bell products, according to officials.

All three of the Blue Bell plants remain closed as the company cleans and sanitizes the facilities.

"Unfortunately, we do not yet have a firm timeline for when Blue Bell ice cream will be back in stores, but we believe at this time that it will be several months at a minimum," said Blue Bell CEO and President Paul Kruse in a statement.

All Blue Bell products were recalled in April.The Associated Press contributed to this report.